The present invention relates to fiber optic cable components and, more particularly, to a fiber optic cable components with markings thereon and methods of making the markings.
Conventional fiber optic cables include optical fiber containing components, for example, optical ribbons or fiber bundles. Optical fibers conduct light which is used to transmit voice, video, and data information. Additionally, fiber optic cables include non-optical fiber containing components, for example, rods, strength members, tapes, etc. The optical fibers in an optical ribbon or fiber bundle are generally encased in a matrix coating of an ultraviolet (UV) light curable type. Typically, such a matrix coating is extruded about a group of optical fibers that have been arranged in an array, and is then cured by irradiation with a UV light source. The cured matrix coating protects the optical fibers and generally fixes the alignment of the respective optical fibers in the array.
Optical fibers may be arranged in an array of the optical ribbon type. FIG. 1 shows adjacent optical ribbons 12-1 and 12-2 of a conventional ribbon stack 12. Optical ribbons 12-1,12-2 each include optical fibers 15 encased in a matrix coating 19. A craftsman may gain access to optical ribbons 12-1,12-2 by cutting away portions of a cable to expose ribbon stack 12. Once stack 12 is exposed, the craftsman may desire to distinguish between and classify the ribbons according to, for example, which telecommunications circuit they are to be associated with. To classify the ribbons, the craftsman may look for markings which uniquely identify the ribbon, for example, a series of alpha-numeric characters which define a label or indicia 16. Indicia 16 includes a series of printed dots 17 which depict the alpha-numeric characters. Dots 17 are small masses of thermal, solvent, or UV curable ink material which present unevenness, e.g., bump-like and/or trough-like (not shown) irregularities on and/or in the surface of matrix coating 19 (FIG. 2). Where ribbons 12-1,12-2 include essentially permanent indicia 16, the craftsman""s ribbon classification task may be done with ease and reliability. It is therefore desirable that indicia 16 be essentially permanent, i.e., robust enough to withstand direct abrasion, or protected by an anti-abrasion overcoating.
Known markings of the printed ink type are printed on the matrix coating of an optical fiber array, or directly on the optical fibers, but such markings may have disadvantages. U.S. Pat. No. 5,485,539, incorporated by reference herein, discloses printed ink dots on a matrix coating that define layered dots that form symbols, and a transparent, anti-abrasion coating may be applied over the printed ink dots. U.S. Pat. No. 5,119,464 discloses a process for directly marking optical fibers with ink as they move in an array, before being coated with a protective envelope, so that staggered bands of ink are formed on the optical fibers. Disadvantageously, however, the printed ink type markings may be removed by a solvent when the ink is on the surface, the print of a ribbon or bundle may be transferred to an adjacent ribbon, and/or the printed ink dots may cause an undesirable level of attenuation loss in the optical fibers.
Laser marking techniques have been developed to mark fiber optic cable components (e.g., cable jackets), but cause substantial ablation of portions of the cable jacket. Substantial laser ablation of fiber optic cable components can result in undesirable physical damage of such components, for example, optical ribbons or bundles. A known laser marking technique is used to mark optical cable jackets formed of a robust, black polyethylene material suited to the outdoor environment, as disclosed in U.S. Pat. No. 5,049,721, incorporated by reference herein. Substantial laser ablation causes physical damage in the form of craters in the black polyethylene jacket. A colored wax of a contrasting color is packed into the craters. The contrasting color wax defines a dot matrix of an alpha-numeric configuration; however, this configuration may not be essentially permanent, as the colored wax may be rubbed off or otherwise become dislodged or flow out of the craters. The physical damage associated with substantial laser ablation of this kind is not particularly suited for use with optical ribbons or bundles, as the laser would likely punch holes through the optical ribbon and destroy the optical fibers. Moreover, ablated craters can negatively affect the robustness of a thin matrix coating.
Multi-layer cable jackets having laser markable surfaces are expensive, and can be too large for application to optical ribbons, individual optical fibers, or fiber bundles. A laser marking method for use with a fiber optic cable having an outer jacket with inner and outer varnish layers is disclosed in U.S. Pat. No. 5,111,523, and is incorporated by reference herein. The inner and outer varnish layers require specialized formulations that are applied around the entire circumference of the fiber optic cable jacket. The thickness of the outer layer is greater than 5 xcexcm and less than 25 xcexcm, and it is intended to be transformed superficially only at the point of laser impact so as to leave a mark which is darker than the inner varnish layer by virtue of its pigment being transformed. The outer layer may be ablated thereby revealing the inner layer, of a minimum thickness between 15-25 xcexcm, which reflects the laser radiation. The transformation or ablation can result in substantial physical damage to the outer varnish layer. Additionally, the two-layer method of marking a fiber optic cable jacket is expensive, and, given size constraints, may not be suitable for application on an optical fiber ribbon, individual optical fibers, or fiber bundles.
It is an object of the present invention to provide a fiber optic cable component comprising a radiation markable section including a radiation reactive ingredient, exposure to a radiation source causing a marking to be made in the radiation markable section so that physical damage to the layer by the radiation is avoided. The radiation reactive ingredient can, for example, be selected from the group of photoreactive ingredients consisting of an inorganic compound, a metal salt, a radiation reactive dye, a silver halide material, and a photoreactive acrylate material.
It is another object of the present invention to provide a method of marking a fiber optic cable component, comprising the steps of irradiating a radiation markable section on a fiber optic cable component with a radiation source and causing a photochemical reaction in the radiation markable section whereby a marking is made in the radiation markable section that contrasts with a color of another material so that physical damage to the radiation markable section by the radiation is avoided. The method may utilize a laser as a source of radiation.